This invention relates generally to novel polymers exhibiting electrical conductivity and electrically conductive films formed therefrom, and more particularly to peripherally modified polymers which exhibit isotropic electrical conductivity.
Because of their elasticity and plasticity, electrically conducting polymers have certain significant advantages over metallic and other non-polymeric electrical conductors and semiconductors. However, some of the more commonly employed polymeric conductors such as polypyrrole, polythiophenes, polyanilines, polyacetylenes and polyarylenes have certain disadvantages such as lower than desired electrical conductivity, air-sensitivity, moisture-sensitivity, and do not always exhibit the desired elasticity and plasticity properties. For example, the most popular electrically conductive polymer, polyacetylene, does not exhibit good electrical conductivity unless it is doped, i.e., reacted with electron acceptors or donors and the resulting highly electrically conductive polyacetylene derivatives are in general highly sensitive to the environment and rapidly loose their initial electrical conductivity in the presence of air and/or moisture. Additionally, polyacetylene is insoluble and infusible and therefore cannot be easily formed into desired shapes.
In order to overcome some of the undesirable properties of polyacetylenes, such as air-sensitivity, moisture-sensitivity, insolubility, and infusibility, various substituted polyacetylenes in which one or both of the hydrogen atoms is replaced by another element or group have been synthesized. While certain substituted polyacetylenes have exhibited high oxygen stability and the ability to be cast as films from solution, they have in general proved to be disappointing with respect to their electrical properties, with typical conductivities being in the range of 10.sup.-16 to 10.sup.-18 S cm.sup.-1. Doping of the substituted polyacetylenes such as with iodine improves the conductivity up to the range of from about 10.sup.-6 to about 10.sup.-3 S cm.sup.-1, but these values are much inferior to those of doped polyacetylene. Other conducting polymers generally have electrical conductivities which are considerably lower than that of doped polyacetylene and/or have other important disadvantages. Accordingly, there remains a need for electrically conductive polymers which have electrical conductivities comparable to that of doped polyacetylene, and which are castable and environmental stable.
Recently, attention has been directed toward the construction of macromolecular complexes from cationic polymers and monomeric anion radicals to produce conductive polymers having .pi.-stacks of organic ion radicals or charge transfer complexes. For example U.S. Pat. No. 5,272,217 discloses a polymeric complex comprised of a quaternized cationic polyamine which is combined with N,N-bis(4,-hydroxysulfonylphen-1'-yl)-1,4,5,8-naphthalenetetracarboxylic acid diimide disodium salt. The complex is precipitated as a solid or deposited as a film by electro-precipitation. The resulting complex exhibits highly anisotropic electrical conductivity which is generally several orders of magnitude lower than that of doped polyacetylene.